1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing apparatus for processing a glass substrate and a semiconductor substrate used for a liquid crystal display device and so forth.
2. Description of the Related Art
In a producing process for a liquid crystal display (LCD), a photolithography technology for producing a semiconductor device is also used to form an indium tin oxide (ITO) thin film and an electrode pattern on a glass substrate for an LCD. In the photolithography technology, photoresist is coated on a glass substrate. Thereafter, the photoresist on the glass substrate is exposed and developed.
As an example of the exposing method, a so-called half-exposing method is known. In the ordinary exposing method, a portion not to be exposed is covered with a mask so as to insulate it from light. In contrast, in the half-exposing method, a half-tone mask or the like that has regions with different transmittances. With the half-tone mask, a region whose exposure amount is smaller than the other regions, namely, a region whose exposure depth is smaller than the other regions can intentionally be formed. As a result, the exposure depths of regions can be varied like a region covered with a mask (namely, a fully exposed region), a region covered with a half-tone mask (namely, a lightly exposed region), and a region that is covered with a mask (namely, a non-exposed region). As a result, with one mask, a film having different resist film thicknesses can be formed. As a result, the half-exposing method allows the number of masks to be decreased. Consequently, the process time necessary for replacing masks can be shortened (as disclosed in for example Japanese Patent Laid-Open Publication No. HEI 09-080740 paragraphs 0002, 0003, and so forth).
A half-tone mask has a plurality of half-light insulating regions of the same shape and same area. Thus, the depths and widths of half-exposed regions have to be the same.
However, actually, when a photoresist is half-exposed, the depths and widths of half-exposed regions vary. As a result, a residual film of the developed resist becomes nonuniform. In other words, the aspect ratio and pitch of the developed resist pattern become nonuniform. In reality, the residual film of the developed resist deviates by 10 percent or more against a desired value. Thus, the distances of a plurality of electrodes that have etched become nonuniform. As a result, switching times of different regions of one device vary. Thus, when a picture is displayed on for example an LCD, color shading and so forth result in.